AIMS:Nitric oxide (NO), is a simple but multifarious molecule. It is implicated in physiological and pathological processes within the striatum, mainly in the nucleus accumbens (NAc). The aim of the present study was to determine the origin of NO in the NAc of anaesthetized rats by applying various compounds known to modulate the release of NO when applied either systemically or locally. MAIN METHODS:Real-time monitoring of NO was carried out by introducing an amperometric NO sensor into the outer tubing of a push-pull cannula. For local application of substances, the push-pull superfusion technique was used. KEY FINDINGS:An overdose of urethane (i.p.) or superfusion of the NAc with tetrodotoxin (TTX) led to a fall of NO release in the NAc. The NO synthase (NOS) inhibitors 7-nitroindazolmonosodiumsalt (7-NINA, neuronal NOS selective) and N-nitro-L-arginine (L-NNA, NOS selective) decreased release of NO when applied i.p. or locally. Superfusion of the NAc with N-methyl-D-aspartate (NMDA) elicited a dose dependent increase of NO release. SIGNIFICANCE:Combination of an amperometric NO sensor for real-time monitoring of NO release with the push-pull superfusion technique showed that NO released in the NAc is, at least to a great extent, of neuronal origin. The enhanced release of NO elicited by locally applied NMDA demonstrates that activation of NMDA receptors facilitates NO synthesis, thus underlining the functionality of NO targets within the NAc.

Pretreatment with mGluR1 antagonist AIDA (1 mg/kg) nearly completely prevented the onset of tonic-clonic seizures and increased generation of NO in the cerebral cortex of rats with genetically determined audiogenic reaction to acoustic stimulation. Administration of mGluR5 antagonist MPEP (10 mg/kg) before audiogenic exposure was followed by a significant decrease in the degree of seizure and partially prevented increased generation of NO due to acoustic stimulation. These data indicate that mGlu receptors and NO play an important role in the pathogenetic mechanisms of audiogenic seizures.

Aims: Thalamostriatal fibers are involved in cognitive tasks such as acquisition, learning, processing of sensory events, and behavioral flexibility and might play a role in Parkinson's disease. The aim of the present study was the in vivo electrochemical characterization of the projection from the lateral aspect of the parafascicular thalamus (Pfl) to the dorsolateral aspect of the nucleus accumbens (dNAc). Since nitric oxide (NO) plays a crucial role in striatal synaptic transmission, its implication in Pfl-evoked signaling within the dNAc was investigated. Main methods: The Pfl was electrically stimulated utilizing paired pulses and extracellular potentials were recorded within the dNAc. Simultaneously, the dNAc was superfused using the push-pull superfusion technique for local application of compounds and for assessing the influence of NO on release of glutamate, aspartate and GABA.Key findings: Stimulation of the Pfl evoked a negative-going component at 9-14 ms followed by a positive-going component at 39-48 ms. The early response was current-dependent and diminished by superfiision of the dNAc with tetrodotoxin, lcynurenic acid or N-G-nitro-L-arginine methyl ester (L-NAME), while 3-(2-hydroxy-2-nitroso1 -propylhydrazino)-1-propanamine (PAPA/NO) increased this evoked potential. Transmitter release was inhibited by L-NAME and facilitated by PAPA/NO.Significance: This study describes for the first time in vivo extracellular electrical responses of the dNAc on stimulation of the Pfl. Synaptic transmission within the dNAc on stimulation of the Pfl seems to be facilitated by NO. (c) 2014 Elsevier Inc. All rights reserved.

Background and Purpose The influence of the neurotransmitter histamine on spontaneous and stimulation‐evoked release of glutamate, aspartate, GABA and ACh in the nucleus accumbens ( NAc ) was investigated in vivo . Experimental Approach Using the push–pull superfusion technique, histaminergic compounds were applied to the NAc and neurotransmitter release was assessed. In some experiments, the fornix/fimbria of the hippocampus was electrically stimulated by a microelectrode and evoked potentials were monitored in the NAc . Key Results Superfusion of the NAc with the H 1 receptor antagonist triprolidine (50 μ M ) decreased spontaneous outflow of glutamate, aspartate and ACh , while release of GABA remained unaffected. Superfusion with histamine elevated release of ACh , without influencing that of the amino acids. Electrical stimulation of the fornix/fimbria enhanced the output of amino acids and ACh within the NAc . The evoked outflow of glutamate and ACh was diminished on superfusion with triprolidine, while release of aspartate and GABA was not affected. Superfusion of the NAc with histamine intensified the stimulation‐evoked release of glutamate and A ch. Histamine also elevated the stimulation‐induced release of aspartate, without influencing that of GABA . Presuperfusion with triprolidine abolished the reinforced effect of histamine on stimulation‐evoked transmitter release within the NAc . Conclusion and Implications Neuronal histamine activates H 1 receptors and increases spontaneous release of glutamate, aspartate and ACh within the NAc . Stimulation of the hippocampal fornix/fimbria tract also enhances release of glutamate and ACh within the NAc and this effect is intensified by H 1 receptor stimulation within the NAc . The latter effects, which are mediated by hippocampal afferences, might play an important role in mnemonic performance and in emotional processes such as anxiety and stress disorders. Linked Articles This article is part of a themed issue on Histamine Pharmacology Update. To view the other articles in this issue visit http://dx.doi.org/ 10.1111/bph.2013.170.issue‐1

Background and PurposeHere, we have investigated whether learning and/or short‐term memory was associated with release of ACh and glutamate in the rat nucleus accumbens (NAc). Additionally, neurotransmitter release in the NAc was assessed during facilitation of cognitive processes by antagonists of inhibitory histamine autoreceptors.Experimental ApproachThe olfactory, social memory test was used in combination with push–pull superfusion of the NAc. A male, juvenile rat was exposed twice to an adult male rat at intervals of 60 or 90 min, and release of ACh and glutamate was determined in the NAc of the conscious adult rat. Histamine receptor antagonists were applied i.c.v.Key ResultsFirst exposure of a juvenile rat to an adult rat increased ACh and glutamate release in the NAc of the adult rat. Repetition of exposure after 60 min did not change release of ACh and glutamate, while contact time to recognition (CTR) was shortened. Repetition of exposure after an interval of 90 min prolonged CTR and enhanced accumbal ACh and glutamate release rates. Injection (i.c.v.) of thioperamide (histamine H3 receptor antagonist) together with famotidine (H2 receptor antagonist), 80 min prior to second exposure, diminished CTR and abolished ACh and glutamate release when second exposure was carried out 90 min after the first one.Conclusions and ImplicationsHistaminergic neurons per se facilitated short‐term memory, without activation of cholinergic and/or glutamatergic neurons in the NAc of rats. Cholinergic and glutamatergic neurons within the NAc contributed to learning but not to recall of memory.Linked ArticlesThis article is part of a themed issue on Histamine Pharmacology Update. To view the other articles in this issue visit http://dx.doi.org/ 10.1111/bph.2013.170.issue‐1

In a previous study the simple, naturally derived coumarin scopoletin (SCT) was identified as an inhibitor of acetylcholinesterase (AChE), using a pharmacophore-based virtual screening approach. In this study the potential of SCT as procholinergic and cognition-enhancing therapeutic was investigated in a more detailed way, using different experimental approaches like measuring newly synthesized acetylcholine (ACh) in synaptosomes, long-term potentiation (LTP) experiments in hippocampal slices, and behavior studies. SCT enhanced the K+-stimulated release of ACh from rat frontal cortex synaptosomes, showing a bell-shaped dose effect curve (E(max): 4 μM). This effect was blocked by the nicotinic ACh receptor (nAChR) antagonists mecamylamine (MEC) and dihydro-β-erythroidine (DHE). The nAChR agonist (and AChE inhibitor) galantamine induced a similar increase in ACh release (E(max): 1 μM). SCT potentiated LTP in hippocampal slices of rat brain. The high-frequency stimulation (HFS)-induced, N-methyl-D-aspartate (NMDA) receptor dependent LTP of field excitatory postsynaptic potentials at CA3-CA1 synapses was greatly enhanced by pre-HFS application of SCT (4 μM for 4 min). This effect was mimicked by nicotine (2 μM) and abolished by MEC, suggesting an effect on nAChRs. SCT did not restore the total inhibition of LTP by NMDA receptor antagonist D, L-2-amino-5-phosphonopentanoic acid (AP-5). SCT (2 μg, i.c.v.) increased T-maze alternation and ameliorated novel object recognition of mice with scopolamine-induced cholinergic deficit. It also reduced age-associated deficits in object memory of 15-18-month-old mice (2 mg/kg sc). Our findings suggest that SCT possesses memory-improving properties, which are based on its direct nAChR agonistic activity. Therefore, SCT might be able to rescue impaired cholinergic functions by enhancing nAChR-mediated release of neurotransmitters and promoting neural plasticity in hippocampus.

Background Numerous studies support an important contribution of endogenous opioid peptide systems in the mechanisms of emotional behavior. It is well known that the structure of opioid receptors (OR) and endogenous opioid peptides in the CNS and in the periphery is identical, but the central and peripheral functions of endogenous opioid systems are considered different, because the blood-brain barrier (BBB) generally prevents the entry of peptides into the brain. We hypothesize that the central and peripheral components of the endogenous opioid system function in close relationship, interacting with each other. The aim of this work was to study an influence of a peripheral administration of the μ opioid receptor ligands, which do not penetrate the BBB, on behavioral parameters as well as on extracellular levels of b-endorphin (BE) in the the cingulate cortex (CC) of rats during acute emotional stress.

Background Drug abuse among pregnant women continues at alarming frequency. Exposed children often show selective impairments of attention and other disturbances which might develop to major cognitive disorders. This work seeks to examine the impact of prenatal stress (PS) induced by the psychostimulant drug amphetamine (AMPH) on memory functions in male offspring of rats and to study the possible neuroprotective action of the novel Russian peptide Semax (a synthetic analogue of ACTH4-7). In addition, the role of the neuronal messenger nitric oxide (NO) as well as the intensity of lipid peroxidation (LPO) in mechanisms of PS was examined.

The psychostimulant amphetamine (AMPH) has been found to induce striatal acetylcholine release and neurotoxic processes via nitric oxide (NO) and lipid peroxidation (LPO). Our purpose was to determine whether blocking striatal muscarinic (M1) receptors by the selective M1 antagonist toxin 7 (MT 7; bilaterally, 2 μg per side) might attenuate the effects of AMPH (4 × 5 mg/kg, i.p.). Systemic AMPH administration increased NO and LPO in the striatal tissue. Stimulation of M1 receptors by i.c.v. injection of M1 agonist McN‐A‐343 (200 μg) caused a similar enhancement of NO and LPO. Pretreatment with the MT7 prevented the AMPH‐induced NO generation and greatly reduced the LPO caused by the psychostimulant. These results show that M1 acetylcholine receptors are critically involved in neurotoxic processes induced by AMPH via NO and LPO.

Background Among the chemical class of coumarins several substances have been described to be effective as cognition enhancers. We have recently characterized the coumarin scopoletin as a compound which fits a pharmacophore model of AChE inhibitors and enhances the release of ACh in rat brain [1]. Now, a comprehensive study was carried out in order to investigate the effects of scopoletin on learning and memory, on release of ACh from synaptosomes and on hippocampal long-term potentiation (LTP) in order to uncover the mechanism of action.

Background Parkinson's disease (PD) is one of the most widespread neurodegenerative diseases. A reduction of complex I activity has been demonstrated in mitochondria of PD patients. Recently, it was shown that chronic subcutaneous exposure to low doses of rotenone (an inhibitor of mitochondrial NADH dehydrogenase and a commonly used pesticide) caused highly selective nigrostriatal dopaminergic lesions. However, while the behavioural effects of rotenone administration are well characterised, the mechanisms underlying rotenone action are unclear. Recent studies are regarding nitric oxide (NO) as universal neuronal messenger in the pathophysiology of neurodegenerative diseases. The aim of this work is to study mechanisms underlying oxidative damage of the various brain areas of rats produced by rotenone and to investigate a possible role of NO and lipid peroxidation (LPO) processes during chronic rotenone administration.

The psychostimulant amphetamine (AMPH) has been found to induce striatal acetylcholine release and neurotoxic processes via nitric oxide (NO) and lipid peroxidation (LPO). Our purpose was to determine whether blocking striatal muscarinic (M1) receptors by the selective M1 antagonist toxin 7 (MT 7; bilaterally, 2 μg per side) might attenuate the effects of AMPH (4 × 5 mg/kg, i.p.). Systemic AMPH administration increased NO and LPO in the striatal tissue. Stimulation of M1 receptors by i.c.v. injection of M1 agonist McN-A-343 (200 μg) caused a similar enhancement of NO and LPO. Pretreatment with the MT7 prevented the AMPH-induced NO generation and greatly reduced the LPO caused by the psychostimulant. These results show that M1 acetylcholine receptors are critically involved in neurotoxic processes induced by AMPH via NO and LPO.

Acetylcholinesterase (AChE) inhibition is today the main strategy in the clinical management of Alzheimer's disease. Its benefits extend from early stages of various dementia types into Parkinson's disease, ataxia, and myasthenia gravis1. Natural products have already established themselves as an excellent source for AChE inhibiting compounds (e.g. galantamine, huperzine A), but new substances with better efficacy and less side effects are still demanded2. While performing a screening of extracts from our plant collection using an enzyme assay with Ellman's reagent3, preparations made of sumac (Cotinus coggygria Scop., Anacardiaceae) were shown to inhibit AChE; the most potent was the methanol extract of the heartwood (IC50 of 89.3µg/ml; CI95 72.4–108.7µg/ml). Subsequent tests pointed to the ether partition as most active fraction of the above extract (IC50 of 25.4µg/ml; CI95% 20.8–32.2µg/ml). Bioactivity-guided isolation highlighted sulfuretin, its main component, as active compound (IC50 of 29.9µM; CI95% 26.4–33.7µM). Following these positive preliminary results, we investigated in vivo the ability of sumac extracts to enhance cholinergic transmission in the brain, using the push-pull technique. Injection into the ipsilateral cerebral ventricle of 10mg/kg ether partition increased the extracellular acetylcholine concentration in rat brain to about 220% compared to basal release. These are the first in vivo results demonstrating the elevation of cerebral acetylcholine level by an aurone-enriched C. coggygria fraction.

Leontopodium alpinum ('Edelweiss') was phytochemically investigated for constituents that might enhance cholinergic neurotransmission. The potency to increase synaptic availability of acetylcholine (ACh) in rat brain served as key property for the bioguided isolation of cholinergically active compounds using different chromatographic techniques. The dichlormethane (DCM) extract of the root, fractions and isolated constituents were injected i.c.v. and the effect on brain ACh was detected via the push-pull technique. The DCM extract enhanced extracellular ACh concentration in rat brain and inhibited acetylcholinesterase (AChE) in vitro. The extracellular level of brain ACh was significantly increased by the isolated sesquiterpenes, isocomene and 14-acetoxyisocomene, while silphiperfolene acetate and silphinene caused a small increasing tendency. Only silphiperfolene acetate showed in vitro AChE inhibitory activity, thus suggesting the other sesquiterpenes to stimulate cholinergic transmission by an alternative mechanism of action. Isocomene was further investigated with behavioural tasks in mice. It restored object recognition in scopolamine-impaired mice and showed nootropic effects in the T-maze alternation task in normal and scopolamine-treated mice. Additionally, this sesquiterpene reduced locomotor activity of untreated mice in the open field task, while the activity induced by scopolamine was abolished. The enhancement of synaptic availability of ACh, the promotion of alternation, and the amelioration of scopolamine-induced deficit are in accordance with a substance that amplifies cholinergic transmission. Whether the mechanism of action is inhibition of AChE or another pro-cholinergic property remains to be elucidated. Taken together, isocomene and related constituents of L. alpinum deserve further interest as potential antidementia agents in brain diseases associated with cholinergic deficits.

An assay was set up for glyceryl ether monooxygenase activity in tissue samples using the novel substrate 1-O-pyrenedecyl-sn-glycerol and high-performance liquid chromatographic analysis of reaction mixtures with fluorescence detection, allowing robust detection of enzymatic activity in microgram amounts of tissue homogenates. The activity partially purified from rat liver strictly depended on the presence of a tetrahydropteridine. Tetrahydrobiopterin-dependent glyceryl ether monooxygenase activity was observed in all rat tissues tested except female heart, with highest activities in liver, intestine, and cerebellum. Activity was not uniformly distributed in brain: it was higher in cerebellum than in striatum or cortex. These data demonstrate that tetrahydrobiopterin-dependent glyceryl ether monooxygenase is found not only in liver and the gastrointestinal tract but also in brain and other organs of the rat and provide an additional goal for tetrahydrobiopterin biosynthesis in these organs.